1. Field of the Invention
The present invention relates to an apparatus for measuring micro-cracks in a membrane electrode assembly and a method for predicting the generation of micro-cracks in the membrane electrode assembly and, more particularly, to an apparatus for measuring micro-cracks in the membrane electrode assembly for a fuel cell, which is formed on an upper surface and a lower surface thereof, and includes an upper conductive catalytic layer and a lower conductive catalytic layer, respectively, and a method for predicting the generation of micro-cracks in the membrane electrode assembly.
2. Description of the Related Art
A stack for a fuel cell is generally comprised of hundreds of unit cells. Each unit cell includes, for example, a Membrane Electrode Assembly (MEA), a Gas Diffusion Layer (GDL), and a separator, and plays an important role in the generation of electricity. Among the constituent components of the unit cell, electrodes of the membrane electrode assembly are formed on respective surfaces of the membrane electrode assembly, i.e. the upper surface and the lower surface thereof. These electrodes are present in a Pt/C form, in which the surfaces of carbon particles are covered with a catalyst such as, for example, platinum. Substantially, a chemical reaction occurs when supplied reaction gas, i.e. hydrogen, oxygen, or air including the same meets the catalyst layer, thus generating water and electricity, which are the outputs of the reaction.
FIG. 1 (RELATED ART) is a view illustrating the basic configuration of a membrane electrode assembly for a fuel cell, and FIG. 2 (RELATED ART) is an SEM analytic image illustrating the configuration of the membrane electrode assembly for the fuel cell.
The membrane electrode assembly, as exemplarily illustrated in FIG. 1, includes a polymer electrolyte membrane, which transfers protons, and catalyst layers which are present in the form of coatings on both surfaces of the polymer electrolyte membrane. Each of the catalyst layers consists of an electrically conductive carbon support and a platinum catalyst.
The catalyst layers exhibit structural vulnerability, particularly, under severe fuel cell operating conditions, and are susceptible to the generation of micro-cracks as the operating time increases. Once the micro-cracks have been generated, the micro-cracks become large cracks as time passes.
For example, when the stack of the fuel cell repeatedly experiences a cyclic dry/wet or freezing/thawing environment, micro-cracks are first generated in the catalyst layers. Then, the cracks grow as the operating time increases, thereby consequently having a very negative effect on the durability of the stack.
That is, although the generation of micro-cracks in the catalyst layers has been recognized as an important factor that may determine the lifespan of a fuel cell vehicle, technical developments to quantitatively and accurately evaluate the generation and growth of micro-cracks have not been implemented according to the related art.
Meanwhile, various methods for measuring micro-cracks have been proposed and used in the related art. For example, micro-cracks have been measured via various nondestructive inspection methods such as, for example, ultrasonic inspection, radiographic inspection, liquid permeation inspection, and thermal inspection methods.
However, these nondestructive inspection methods merely verify the presence of cracks, but cannot measure the generation and growth of micro-cracks, and thus are difficult to apply to composite materials, such as the membrane electrode assembly for the fuel cell.